1. Field of the Invention
The present invention relates to oil and gas wellbore completion. More particularly, the invention relates to a system of completing a wellbore through the expansion of tubulars. More particularly still, the invention relates to methods for expanding a section of coiled tubing into a surrounding tubular so as to form a patch.
2. Description of the Related Art
In the drilling of oil and gas wells, a wellbore is formed using a drill bit that is urged downwardly at a lower end of a drill string. After drilling a predetermined depth, the drill string and bit are removed and a section of casing is lowered into the wellbore. An annular area is thus formed between the string of casing and the formation. The casing is temporarily hung from the surface of the well. A cementing operation is then conducted in order to fill the annular area with cement. Using apparatus known in the art, the casing is cemented into the wellbore by circulating cement into the annular area defined between the outer wall of the casing and the borehole. The combination of cement and casing strengthens the wellbore and facilitates the isolation of certain areas of the formation behind the casing for the production of hydrocarbons.
It is common to employ more than one string of casing in a wellbore. In this respect, a first string of casing is set in the wellbore when the well is drilled to a first designated depth. The first string of casing is hung from the surface, and then cement is circulated into the annulus behind the casing. The well is then drilled to a second designated depth, and a second string of casing, or liner, is run into the well. The second string is set at a depth such that the upper portion of the second string of casing overlaps the lower portion of the first string of casing. The second liner string is then fixed, or xe2x80x9chungxe2x80x9d off of the existing casing by the use of slips which utilize slip members and cones to wedgingly fix the new string of liner in the wellbore. The second casing string is then cemented. This process is typically repeated with additional casing strings until the well has been drilled to total depth. In this manner, wells are typically formed with two or more strings of casing of an ever-decreasing diameter.
In many instances, the casing is perforated, typically at a lower region of the casing string. Alternatively, the last string of casing extending into the wellbore may be pre-slotted to receive and carry hydrocarbons through the wellbore towards the surface. In this instance, the hydrocarbons are filtered through a screened portion of tubular. In either instance, the hydrocarbons flow from the formation, into the wellbore, and then to the surface through a string of tubulars known as production tubing. Because the annulus between the casing and the production tubing is sealed with packers, the hydrocarbons flow into the production tubing en route to the surface.
Over the life of a well, circumstances may occur that change the properties of particular formations. For example, the pressure in a formation may fall, or a formation may begin to produce an unacceptably high volume of water. In these situations, it is known to run straddles into the well to patch the perforations adjacent the troubled formation. Straddles are sections of hard pipe with sealing arrangements at either end. Typically, the straddle is located downhole at the depth of the perforations. The seals are actuated into contact with the surrounding casing to isolate the perforations between the seals.
Additionally, there are varied other uses for a patch or straddle within a live well. For example, a straddle may be used to patch over corroded sections of tubulars within the wellbore, such as production tubing or casing. Straddles may also be used to patch over eroded sections of tubulars or to cover screens in gravel packs. Straddles may further be used to create a restricted flow area thereby increasing the velocity of a fluid during production of the well.
Conventional straddles tend to be complex in operation. A conventional straddle consists of a length of tubular having a mechanical packer at either end. The mechanical packers have moving parts that are expensive to fabricate and install. Conventional straddles require a source of hydraulic and/or mechanical force to actuate the seals. Further, conventional straddles of hard pipe result in a significant loss in bore cross section which chokes off the well, thereby reducing production capacity.
Another problem associated with existing straddles is the time and cost associated with locating and setting a straddle of hard pipe in a live well. Conventional straddles are run into a live well on a string of tubulars. Lowering a string of tubular into a live well requires the use of at least two pressure devices to safely maintain the well while running the tubular string. Such an operation also requires the placement of a large working unit for handling joints of working string. Removal of the string requires the same amount of time and energy.
There is a need, therefore, for an easier and less expensive system for patching or repairing a tubular. There is a further need for an improved assembly for patching or repairing a tubular in a live well. There is further a need for an apparatus and methods by which a section of tubular, such as casing or a sand screen, can be either straddled or patched by expanding a replacement section therein.
The present invention provides methods for expandably installing a section of coiled tubing in situ within a wellbore, including a live wellbore. The installed section of coiled tubing is used to form a patch within a surrounding tubular body. For purposes of the present inventions, the term xe2x80x9cpatchxe2x80x9d includes any installation of a section of coiled tubing into a surrounding tubular body. Such patches include, but are not limited to: (1) the expansion of a section of coiled tubing along a desired length in order to seal perforations; (2) the expansion of coiled tubing above and below perforations in order to form a xe2x80x9cstraddle;xe2x80x9d and (3) the expansion of a section of coiled tubing at a point above perforations in order to form a xe2x80x9cvelocity tubexe2x80x9d and to isolate an upper portion of surrounding casing. The patch may also serve to support a corroded or weakened section of tubular. In any method of the present invention, the surrounding tubular body may comprise a string of production tubing, a string of casing, a sand screen, or any other tubular body disposed within a wellbore.
In the methods of the present invention, an assembly is run into the wellbore on a working string. The assembly in one aspect comprises a slip, a motor, a cutting tool, and an expander tool. In operation, the assembly is lowered into the wellbore on a string of coiled tubing. A section of coiled tubing to be expanded is located in the wellbore at the desired depth. The expander tool is then actuated, preferably through the use of hydraulic pressure, so as to expand the section of coiled tubing into a surrounding tubular. Thereafter, the coiled tubing is cut above the expanded region, thereby leaving a patch within the wellbore. The patch remains in the wellbore through frictional engagement with the surrounding tubular. The expansion assembly is then removed from the wellbore, along with the unexpanded portion of coiled tubing above the severance point.
In an alternate aspect of the invention, a method is provided which installs a patch into a wellbore as outlined above. Then, a new expansion assembly is run into the wellbore. The second expansion assembly is disposed within a working string, and is run into the wellbore adjacent the patch. The second expansion assembly in one aspect comprises a slip, a motor, a telescoping member, and rotating expander tool. The expander tool is actuated so as to expand additional lengths of the patch. At the same time, the telescoping member is actuated to translate the expander tool in order to extend the length of the patch within the wellbore. Alternatively, or in addition, the expander tool is translated by raising or lowering the working string from the surface.
In a further aspect, a method is provided which comprises providing coiled tubing which has been severed into an upper section and a lower section. An expansion assembly is then assembled which comprises a first slip, a second slip, a motor, a telescoping member, a cutting tool, a first expander tool, and a second expander tool. The first slip is activated to engage the upper section of coiled tubing. Similarly, the second slip is activated to engage the lower section of coiled tubing. The first and second slip of the expansion assembly are positioned together so that the upper and lower sections of coiled tubing are joined. In this manner, a continuous length of coiled tubing is essentially formed. The expansion assembly is run into the wellbore on the coiled tubing. The second expander tool is actuated to partially expand the lower section of tubing into frictional engagement with the surrounding casing in the wellbore. The second expander tool is de-activated, and the second slip is also then de-activated. The upper section of coiled tubing is then raised so as to align the first expander tool substantially with the upper end of the lower section of coiled tubing. The first expander tool is then actuated so as to begin expanding the lower section of tubing into the surrounding casing. At the same time, the expansion assembly is translated within the wellbore so as to form a patch of a desired length.
In one aspect, the first expander tool is configured to have pitched rollers. The pitched rollers cause the expansion assembly, including the first expander tool, to xe2x80x9cwalkxe2x80x9d downward within the wellbore as the first expander tool is rotated. In another aspect, the first expander tool is further translated by actuating the telescoping member. After the patch has been fully formed, the upper section of coiled tubing is retrieved from the hole, thereby removing the expansion assembly as well.